1. What is a seizure A burst of action potentials The epileptic focus The neuronal network in epilepsy The latest theory

2. What is a seizure? “abnormal synchronization, excessive excitation and/or inadequate inhibition, … can affect small or large neuronal populations.”

3. A burst of action potentials sustained neuronal depolarization resulting in a burst of action potentials, plateau-like depolarization associated with completion of the action potential burst, rapid repolarization followed by hyperpolarization. paroxysmal depolarizing shift

4. The epileptic focus Where the activity begins Aka seizure onset zone Traditionally, the epileptic focus was supposed to be spatially restricted. Now imagined to be an extended neuronal network responsible for seizure generation.

5. Generalisation GABA-ergic and hyperpolarised neurons inhibit the epileptogenic neurons When the epileptogenic neurons overcome the surrounding inhibitory influence, the seizure discharge spreads

6. Seizure Threshold Normal = high seizure threshold. Epilepsy = low seizure threshold. –Alcohol –Sleep Deprivation –Stress

7. The latest theory: metabolic Intracranial EEG + metabolic imaging Mitochondrial activity depressed Energy Depressed Frequency of impulses elevated Neurotransmitters also correlate Epilepsy may arise from an abnormal response to tissue injury